The following is an excerpt from “The Gentlemen’s Book of Etiquette, and Manual of Politeness” by Cecil B. Hartley, published by Locke & Bubier in 1875.
ETIQUETTE IN CHURCH.
It is not, in this book, a question, what you must believe, but how you must act. If your conscience permits you to visit other churches than your own, your first duty, whilst in them, is not to sneer or scoff at any of its forms, and to follow the service as closely as you can.
To remove your hat upon entering the edifice devoted to the worship of a Higher Power, is a sign of respect never to be omitted. Many men will omit in foreign churches this custom so expressive and touching, and by the omission make others believe them irreverent and foolish, even though they may act from mere thoughtlessness. If, however, you are in a country where the head is kept covered, and another form of humility adopted, you need not fear to follow the custom of those around you. You will be more respected if you pay deference to their religious views, than if you undertook to prove your superiority by affecting a contempt for any form of worship. Enter with your thoughts fixed upon high and holy subjects, and your face will show your devotion, even if you are ignorant of the forms of that particular church….